Allow remote url to be passed to the ADD instruction within the builder
Fix issue EXPOSE override CMD within builder
Move isUrl to utils.IsURL
Allow to docker build URL
Move the docker build URL form client to server, prepare for GIT support
Implement build from git
Update documentation for docker build
Allow multiple tab/spaces between instructions and arguments
Fix typo in docs
Updated build usage
Remove run from the ADD instruction
Remove run from non-running commmands
Merge branch 'master' into builder_server-3

Conflicts:
	buildfile.go
	commands.go
	docs/sources/api/docker_remote_api.rst
Fix issue with ADD
Add build UT
Merge branch 'master' into builder_server-3

Conflicts:
	utils/utils.go
Removed deprecated file builder_client.go
* Builder: simplify the upload of the build context. Simply stream a tarball instead of multipart upload with 4 intermediary buffers. Simpler, less memory usage, less disk usage, and faster.
* Builder: reorganized unit tests for better code reuse, and to test non-empty contexts
* Builder: added a regression test for #895